The last year or so has certainly been a mixed bag for booksellers. After a holiday season in which Barnes & Noble posted dismal sales while some independent bookstores rejoiced in brisk business, Kobo is now reporting surprisingly strong numbers for its e-reader sales over the past year.

Kobo – owned by Japanese retailer Rakuten but based in Toronto – is reporting that its e-reader sales doubled in 2012, with 4 million of the devices sold in the last six months. That brings the company’s number of registered users up to more than 12 million, which, according to a recent DigiTimes report, means that Kobo now has about 20 percent of the global market for e-readers.

The holiday season was a particularly strong period, the company says, with e-reader sales increasing by almost 150 percent in December.

Here in the US Kobo has aligned itself with the country's independent bookseller through a partnership with the American Booksellers Association. For now, however, Kobo remains a relatively small player in a US market dominated by Amazon, Apple, and Barnes & Noble.

But globally 2012 was a big year for Kobo. In addition to launching three new devices – the Kobo Glo and Mini e-readers and the Arc tablet – Kobo expanded services into Japan, Spain, South Africa, Italy, Portugal, Brazil, and the Netherlands.

In Canada, where the company is based, Kobo appears to be the market leader, reportedly outselling Amazon Canada.

In 2013, the company says that it intends to further its global expansion, with plans to enter the Russian, Chinese, and Indian markets.

Kobo's year-end report also offered a bit of a snapshot of its customers and their buying patterns. According to the report, the "Fifty Shades of Grey" and "Hunger Games" series were the most-read books on Kobo devices; the average Kobo customer bought 20 percent more e-books in 2012 than in 2011; the company sells most books in English, followed by French and Japanese; and romance books are the most popular genre among Kobo customers.